The invention concerns a piston-type power generating maching with a housing containing one or several cylinder-shaped working spaces and with at least one piston moving back and forth parallel to its longitudinal axis in the working spaces, which is connected with a conversion gear by elements penetrating the housing. The known stroked piston machines exhibiting these characteristics, despite their universal use, still have the disadvantage of the back and forth moving piston mass which must be supported in its several points, which results in heavy loads on the entire machine, especially on the crankshaft and its bearings. This disadvantage of the stroking piston machine does not exist in the case of the rotary piston machine, since no back and forth moving gear drive masses are present, however, the known rotary piston or rotating combustion machines have disadvantages which are not present in stroked piston machines. The difficulties of adequate sealing between the rotary piston and the working cylinder wall as well as the cooling of the cylinder in the case of internal combustion engines should be mentioned.